static std::string Sign(const std::string& secret_id,
                        const std::string& secret_key,
                        const std::string& http_method,
                        const std::string& in_uri,
                        const std::map<std::string, std::string>& headers,
                        const std::map<std::string, std::string>& params);

static std::string Sign(const std::string& secret_id,
                        const std::string& secret_key,
                        const std::string& http_method,
                        const std::string& in_uri,
                        const std::map<std::string, std::string>& headers,
                        const std::map<std::string, std::string>& params,
                        uint64_t start_time_in_s,
                        uint64_t end_time_in_s);

std::string GeneratePresignedUrl(const GeneratePresignedUrlReq& req)

typedef enum {
    HTTP_HEAD,
    HTTP_GET,
    HTTP_PUT,
    HTTP_POST,
    HTTP_DELETE,
    HTTP_OPTIONS
} HTTP_METHOD;

qcloud_cos::CosConfig config("./config.json");
qcloud_cos::CosAPI cos(config);

std::string bucket_name = "examplebucket-1250000000";
std::string object_name = "exampleobject";

// Add the bucket name, object key, and HTTP request method.
// Note: users do not need to encode object_name.
qcloud_cos::GeneratePresignedUrlReq req(bucket_name, object_name, qcloud_cos::HTTP_GET);
std::string presigned_url = cos.GeneratePresignedUrl(req);